Hydrogen gas detection device

In a hydrogen gas detection device, light emitted from a light source is irradiated onto a hydrogen sensor whose reflectance (optical reflectance) varies upon contact with hydrogen gas, and the light transmitted through the hydrogen sensor or reflected by a reflective film of the hydrogen sensor is received by an optical sensor. On the basis of the signal output from the optical sensor and indicative of the amount of light received, the hydrogen gas detection device detects leakage of hydrogen gas.